Mailer Daemon is a process running on e-mails servers. It receive and dispatch inbound e-mails to the correct mail boxes. It also emit error messages back to the sender when an e-mail can't be delivered.
Mailer daemon questions should be asked in the Software | email section.
The message you received inform you that the address NO LONGER EXIST !
The causes can be:
The recipient used the ISP provided mailbox and recently chaged his provider. The acount got deleted with the resiliation of service.
The recipient was receiving to many SPAM and changed his address.
Solution: Get in touch with him and ask for his new address.
The recipient used any web-mail service and:
1 - Did not connect for to long resulting in the deletion of his account. The termination delay varies from 60 to 90 days without any connection.
2 - He violated the terms of services by forwarding chain e-mails, using the acount for spamming, or transmited virus infected e-mails.
3 - He did not use a good password, or let someone know it. This resulted in the account een highjacked or stollen.
Someone deleted the acount, or used it in an inappropriate manner resulting it the account termination.
Not much that you can do. You can only hope that that person get a new address and inform you about it.
There is also the remote possibility that your contact list got slightly corrupted, a single bit error maybe, making that address invalid.
Carefully inspect the actual adress for any error.
Try re-sending the message by typing the address instead of using your contact list.
Electro, June 2013
